In many scientific disciplines successful research depends largely on generating voluminous amounts of experimental data for analysis. With the advent of microarrays, autosamplers, and microfluidics, the research laboratory has become largely automated and reduced in size. Nevertheless, accuracy and precision in sample preparation and measurement remain as critical as ever. A problem that has remained in the art, whether due to the pure bulk of sample analysis, or the ever-shrinking scale of the analytical laboratory, or both, is that laboratory researchers and technicians can incorrectly prepare sample reactions. Frequently this occurs during the preparation of multi-well reaction plates, where sample components are in loaded in the incorrect well (e.g., a well is skipped, a sample component is added twice, etc.). See, e.g., U.S. Pat. No. 4,701,754. Compositions and methods are needed in the art for ensuring proper preparation and analysis of sample components.